Draft damper



1940- P. s. MARTIN ET AL 7 2,212,293

DRAFT DAMPER Original Filed Nov. 13, 1935 Jaw *W Patented Aug. 20, 1940 UNITED STATES PATENT OFFICE DRAFT DAIWPER Perry S. Martin, Harrisonburg, and Charles C.

. Turner, Timberville, Va.

4 Claims.

This invention relates to thermostatically controlled dampers forwood-burning stoves of general utility for use where close. temperature control is desirable or necessary and where absolute dependability of operation can be secured with minimum attention.

The principal object of the invention is to provide an easily operable pilot damper in combina- A tion with a main damper connected to open in graduated steps whereby the damper never opens wide enough at any time to supply air in such large quantities as to permit too rapid burning of the wood. In other words, we provide a temperature controlled damper which upon call for additional heat first uncovers a small opening and if this does not yield the needed increase of warmth, thenuncovers a much larger opening. This control permits an accurate brooder temperature control for long periods without attention when burning almost any kind of wood, whether scrap lumber or wood from the wood yard or other fast burning fuel and in all seasons of the year. I

Another object of the invention is to provide a compound damper of extremely simple and sturdy construction which may be made at a very low cost, is easily assembled and. installed, and furthermore may be added to existing equipment with only minor changes.

35 and having its aperture closed by a second flat plate pivoted on the same hinge. The two plates are connected by a long pin or rivet which permits movement of the second plate to open the aperture an appreciable amount without moving the first plate from the collar rim thereby to provide maximum flow of air. The damper is connected to be operated by a thermostat and preferably is set to be held wide open when the stove is cold and so as to close in response to a chosen rise in temperature. If used as a check damper a reverse setting would be necessary, i. e., sothat the damper would be normally closed at low temperatures.

In the drawing:

Figure 1 is a perspective view of a brooder stove with part of the hover broken away to show the mounting of the damper system.

Figure 2 is an elevation of the stove partly broken away for showing the damper in section.

Figure 3 is an enlarged detail front view of the damper, taken on line 33 of Figure 2.

Figure 4 is a sectional view taken on line 44 of Figure 3 and showing the pilot damper open but the main damper closed.

Figure 5 is a sectional view similar to Figure 4 but showing both the main and pilot damper in open position.

Figure 6 is a view similar to Figure 4 but showing both dampers closed.

As will be seen from the drawing the preferre embodiment of our invention consists of a boxlike structure ll! of oblong form and having side walls I! and I2 and front and back walls l4" and :1:

Hi. In the upper part of the front wall I4 is a doorway 22 for feeding fuel to and removing ashes from the fire box 23. The fire box is supplied with combustion air which flows via the intake 24 in the lower part of side wall I I, into the with a central outlet opening having means for attaching to the usual stove pipe 32. To the top edge of the box is secured, permanently or otherwise, a downwardly and outwardly sloping hover 33 having one section hinged at 35 so that it may be raised to expose the door for refueling or removing ashes.

The doorway 22 is of air tight construction having a rather wide outwardly projecting frame 36 which due to its thickness not only resists warping but also prevents the sheet iron front wall l4 from warping under changes of temperature. The door proper 31, hinged, at its upper edge 38, is provided with reinforcing flanges 39 for telescoping over the frame 36 so that when secured shut by means of spring clamps 40 on each side of the frame the door is substantially air tight which condition is quite important if any appreciable degree of control is to be obtained. It will also be noted that the hinged hover section 34 has a cutaway portion so that it may bear against the closed door at 4| to further aid in making the same air tight.

In order further to make the stove of air tight construction throughout the joints are all electro-welded as shown at 44 and 46. of air into the stove is solely through the air in-' let 24 which is under the fairly accurate control of a damper mechanism shown in detail in Figures 3, 4, and 5. The main damper 5i, pivoted at 52, normally lies fiat against the outer end of the short piece of pipe 53, which tilts Thus entry under the hover.

slightly upward in order that the weight of the damper may act to keep the opening tightly closed. In the main damper is a smaller aperture 54 adapted to be covered by the pilot damper 55 which is also pivoted at 52 and is provided with an ear 56 for receiving the hook 51 which is part of the linkage operated by the thermostat 58. The movement of the pilot damper 55 with respect to the main damper is limited by the cotter pin 59 so that if the thermostat calls for more draft than the pilot can give then the main damper begins to open.

Referring to Figure 2 it will be seen that the fire pot 21 welded at its upper rim tothe side and end walls as at M, is spaced from said walls at 60 and 6E so that the cool incoming air flowing toward the louvre like openings 26 prevents the side walls from becoming overheated. The bottom of the fire pot is spaced from the bottom 20 of the stove which in turn is spaced from the floor 2! as already mentioned, thus providing ample heat insulation between the floor and the fire pot. As will be noted in Figure 2 the louvre like openings 26 are stamped out so as todirect the streams of air downwardly into the base of the fire. These louvre like openings are distributed rather uniformly about the fire pot and are of sufficiently small cross sectional area to cause the air to flow downward in small jets thus insuring a sure and even burning on all sides of the fuel. The total cross sectional area of the openings is approximately equal to that of the intake 2 The openings are located a considerable distance above the floor of the fire pot so that ashes may accumulate for several days at a time before rising high enough to affect the flow of air thus providing a stove that requires no attention for days at a time and during very mild weather only about once a week.

The side walls of the fire chamber are provided with ribs as which keep the wood out of contact with the walls and provide passages for the upwardly moving hot combustion gases. At the top is a dished baffle which is spaced slightly at its periphery from the side walls and is provided with a central opening 56 at the downwardly directed apex for permitting creosote and other condensates which drop from the smoke pipe to drain into the fuel bed. A bracket d8 may be placed on each side of the baffle if this is found desirable. The spacing of the bafile from the side walls and the conical shape tends to keep the hot gases in contact with the side walls whereby the walls uniformly conduct a maximum amount of the generated heat out into the entire zone The peripheral spacing of the baffle from the walls is about enough to provide an air passage approximately equal to the outlet 30. The ribs and the baffle prevent the formation of the usual hot spots due to uneven burning and concentration of the hot gases as they flow toward the fiue and they also cause the dissipation of a maximum amount of the heat before it enters the flue. I

The operation of our stove is quite simple consisting in kindling a fire in the fire pot 21, then filling the fire chamber with convenient fuel of admost any description, i. e., green wood or dry wood, or any kind of blocks or pieces of wood that may be found around the barn yard or wood loft. The door 3'1 is then closed and latched tightly by means of the spring latches so, the hover section '34 is lowered into place. Since the stove and the brooding zone are at first relatively cold the .thermostat mechanism 58 at this time will be holding the damper 50 in its wideopen position but as the room and zone heat up the thermostat will permit first the main damper 5i to close and then as the zone gets warmer the pilot damper is allowed to close or partly close. Then the thermostat may be regulated to maintain any desired hover temperature by adjusting the wafer screw 10 in the usual manner. I a i It will be appreciated in View oflFigure' 1 taken with the preceding description that the draft is controlled almost entirely in accordance with the temperature of the air in the brooding zone because very little heat is conducted to the wafer H by the supporting bracket '12 and this can be further reduced if deemed advisable by mounting the thermostat independently of the stove. Furthermore, the wafer can be screened entirely from direct radiation of the stove if found necessary. By placing the hover at the highest edge of the stove almost the entire heat produced by the burning fuel is caught under the hover where it"can be utilized by the chicks.

Although we have'describ'ed our invention as embodied in a brooder stove, it is to be understood that it can be used with great advantage wherever an even'temperature is needed, for example, in tobacco barns, hot houses and even in homes. Our stove overcomes the greatest disadvantage of wood fuel which is its tendencyto burn up quickly and erratically at an unplesant and even dangerous temperature. In overcoming this disadvantage we provide a stove that requires very little attention andone which burns an economic fuel in an economic manner.

This case is a division of our application, Serial Number 49,638, filed on November 13, 1935.

What we claim is:

1. In a wood-burning brooder stove having an air intake opening, a main damper pivoted normally to close said opening and having an aperture therein, a pilot damper pivoted normally to close said aperture, a thermostat connected to control said pilot damper and to open the same when the temperature of the brooding Zone about the stove drops below a predetermined point and a lost motion connection between the pilot damper and the main damper whereby upon a continued call for'hea't the thermostat begins to open the main damper after the pilot damper has opened through a predetermined range.

2. In combination with a stove having an air duct for controlling combustion in the stove, a compound damper comprising a main damper biased to a desired position to control the passage of air through the duct, said main damper having an aperture therein, a secondary damper heated by the stovefor moving the secondary damper to change the rate of air fiow through the air duct and upon failure of the stove to respond to such change to move both dampers to cause a greater change in the rate of air flow.

3. In a stove, in combination with a draft I opening, a damper comprising an aperturedmain plate biased to close said opening, a secondary plate biased to close the aperture in the main plate, a lost motion connection betweenthe two plates and thermostatic means for moving first the secondary plate to open said aperture and then to move both plates to uncover said opening.

4. combination with 'a stove having an air 7 to hold both members in open position when the stove is cold and upon the generation of heat by the stove adapted first to move the apertured member to rest on the collar and then upon continued generation of heat to move the second 5 member to close the aperture.

PERRY S. MARTIN. CHARLES C. TURNER. 

